1. Field of the Invention
The present invention generally relates to a lens driving system of a photographic camera, and more particularly to the system for automatic focusing zone focus camera adjustable in two zones, having an automatic focusing apparatus and a photographic lens and a means for controlling a movement of the lens in response to signals which are outputted by the automatic focusing apparatus.
2. Description of the Related Art
There are various kinds of camera having an automatic focusing apparatus. Among these cameras, a camera having a "zone focus" type focus adjusting apparatus can be categorized as one type of the automatic focusing camera. As a lens driving system of the "zone focus" type focusing camera, the below-mentioned mechanisms are well-known and utilized for the camera at the moment.
(1) A mechanism is that a lens frame supporting a photographic lens is driven by pre-charged force when locking of the lens frame is released, associated with shutter releasing operation. PA1 (2) A mechanism is that the lens frame is driven by force which is transmitted through a shutter releasing button itself on shutter releasing.
The above-mentioned mechanism (1) requires a charging mechanism, so that the lens driving system is complicated due to interconnection with the charging mechanism and becomes costly.
On the other hand, the above-mentioned mechanism (2) has the improved mechanism as compared with the mechanism (1). For instance, the lens driving system, which has been disclosed in Japanese Laid-open Patent Publication No. 61926/1979 and corresponding U.S. Patent No. 4,148,574, issued on Apr. 10, 1979, operates as follows. At an initial state (non-operating state of a camera) the lens support is positioned and retained at a "far" position (a position of the lens focusing on the subject to be photographed located at a certain position relatively far away from the camera) by being urged by a spring and, then the lens is pushed forward to a "near" position by the lever connected with a shutter releasing button when it is depressed. Furthermore, when the enclosed automatic focusing apparatus outputs the signal showing a "far" range, an electromagnet is excited and the lever is attracted to the electromagnet, and then the lever transmitting its motion to the lens support is arrested. That is, the photographic lens is retained at its initial position ("far" position). The lens driving system disclosed by the abovementioned Publication is so designed that the lens moves for focus adjusting only at the time when the subject to be focused exists within the "near" range (area which is relatively close to the camera). In addition to the above, moving of the lens is associated with the motion of the lever actuated manually by the shutter releasing button.
The following introduced system as another example has been disclosed in Japanese Laid-open Patent Publication No. 105712/1982. The system is almost similar to the system described in the above-mentioned publication. The mechanism is as follows. A lens is driven by a lever associated with a manual operation (a shutter releasing operation). When an automatic focusing device detects the subject to be photographed, which exists within the "far" range (area which is relatively far away from the camera), an electromagnet is excited, and a core is pushed out by virtue of the excited electromagnet, so that a lens support itself is arrested by the core of the electromagnet.
The common feature between the above-mentioned arts is that the movement of the lens is associated with the motion of the manual depressing operation given to the shutter releasing button. In this case, the depressing force at the shutter releasing button increases remarkably and the depressing operation makes a photographer feel heavy. Moreover, this system urges a photographer to depress continuously a shutter releasing button after completion of the exposure operation.
Accordingly, the above-mentioned systems for moving the lens must have problems to be solved, respectively.